The calculation of energy gain in central spark ignition and the effects of different parameters on it

Abstract

Summary form only given, as follows. According to the concept of central spark ignition in inertial confinement fusion, a hot central spot(a thermonuclear spark) is formed in the imploding fuel microsphere, which then ignites and initiates a thermonuclear burn wave that propagates to the outer cold fuel layers. Various calculations of DT targets driven by laser and ion beams have shown that, depending on the target design and the driver parameters, either kind of ignition can occur. In this paper for initially compressed DT or D/sub 2/ microspheres, we have assumed that the step-like initial temperature and density profiles have an uniform pressure distribution. So in this research work, the initial fuel configuration is a compressed sphere of uniform pressure, consisting of a hot central spark and a cold outer fuel layer. We found that the spark ignites only if the thermonuclear heating rate exceeds the cooling energy loses (which is dominated by the bremsstrahlung and the electron heat condition) over the region of spark radius. Drawing of H/sub s/(confinement parameter, H/sub s/=/spl rho//sub s/, R/sub s/, /spl rho//sub s/ and R/sub s/ are spark density and radius respectively) versus T/sub s/(spark temperature), has shown admissible values of the spark parameters. By this curve we have shown that the spark ignition in DT fuel can occur, but in D/sub 2/ fuel, the two allowed regions on T/sub s/, H/sub s/ plane, defined separately by the formation and the ignition criterion, do not overlap, which it indicate that the spark ignition of pure D/sub 2/ fuel is not possible. So, for each temperature and density in spark region, we have found optimum size of spark for formation and ignition.